Articulated flexible wave guide bending and sizing mandrel for h plane

ABSTRACT

This invention is directed to an articulated flexible waveguide bending and sizing mandrel for the H-plane form. This mandrel is capable of forming a waveguide inner surface which is free of scratches or burrs and without any flats or sidewall wrinkles in the bend surfaces or along the straight sections. A plurality of individual elements are secured together by separate shear pins which permits the elements to pivot relative to each other. One face is made at an angle in order to permit bends up to 180* with a minimum radius. The minimum radius depends on the size of each element and the angle of the face.

United States Patent John G. Schmitt 2516 Norcross St., Hillcrest Heights, Md. 20031 a Aug. 19, 1968 Mar. 23, 1971 Inventor Appl. No. Filed Patented ARTICULATED FLEXIBLE WAVE GUIDE BENDING AND SIZING MANDREL FOR H PLANE 3 Claims, 5 Drawing Figs.

2,902,078 9/l959 Fuchsetal ABSTRACT: This invention is directed to an articulated flexible waveguide bending and sizing mandrel for the H-plane form. This mandrel is capable of forming a waveguide inner surface which is free of scratches or burrs and without any flats or sidewall wrinkles in the bend surfaces or along the straight sections. A plurality of individual elements are secured together by separate shear pins which permits the elements to pivot relative to each other. One face is made at an angle in order to permit bends up to 180 with a minimum radius. The minimum radius depends on the size of each element and the angle of the face.

PATENTEU HAR23 I87! FIG. I

' INVENTOR JOHN G. SCHMITT By ZQaW AGI-INT wr/ulam-romrzv Alh'll'llQlJL/i'llill l lLEXljllLE WAVE GUHDE BENDHNG AND flllZllhlG MANDL FUR ll PLANE The invention described herein may be manufactured and used by or for the Government of the United States of Amerion for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates to apparatus for bending rectangular tubes, and more particularly to a mandrel for use in affecting small radius seamless bends in rectangular wave guide tubes where the bends are in the ill-plane.

it is well known that waveguides used for transmitting high frequency electromagnetic energy must possess accurate internal dimensions which are uniformly formed and must be provided with an internal finish which possess no internal scratches or burrs which are detrimental to electrical results. l'rieretofore, waveguides have been bent in a spiral having a small radius at the beginning thereof in order to provide a relatively long waveguide over a'short space between operative components of a system. Waveguide bending methods have left untold interior scratches and burrs which are detrimental to electrical results. Other drawbacks have been that the dimensional sizes cannot be repeated nor accurately held; also, inside comers of the waveguide have not always been precisely at good right angles. Further, drawbacks reside in .the fact that previously bent waveguides have sidewall wrinkles. Each of the mentioned drawbacks have an effect on transmission of electromagnetic energy in the previously made waveguide. lt is therefore necessary in affecting bends in waveguides to uniformly support the interior thereof with a flexible mandrel in order to preserve as far as possible the original interior cross-sectional dimensions of the tubes and to size the inner dimensions thereof, where they may be slightly off, while preventing scratching of the interior surface of the waveguide by the supporting mandrel in order to eliminate arcing of the high frequency energy or other unwanted changes in the electrical transmission characteristics of the waveguide.

l-leretofore, flexible mandrel have been used for bending tubular cylindrical tubes wherein the waveguide mandrels in cluded cylindrical/elements within the circular portion of the mandrel elements. Each of the elements in this type mandrel have angular faces over a semicircular section of each element in order to provide bends within the flexible mandrel. Such flexible mandrels are fragile and cannot withstand the pull required to bend rectangular waveguide benders in the liplane. in addition to flexible mandrels for bending cylindrical tubular elements there has been made heretofore a mandrel for making small radius tubular bends in a rectangular waveguide in the E-plane. Such wave guides are not capable of making bends in the ll-plane and are limited in their minimum bends by the construction of the elements which form the mandrel.

it is therefore an object of the present invention to provide an articulated mandrel for supporting the interior of a rectangular waveguide tube during bending the tube in the l-l-plane.

Another object is to provide a mandrel which will substantially eliminate scratches or burrs on the interior surface of a waveguide tube during the bending thereof in the H-plane.

Still another object is to provide a mandrel by which internal uniform dimensions may be maintained for successfully made waveguides while forming good right angle corners in the rectangular waveguide.

Yet another object is to provide a mandrel for making bends in a rectangular waveguide in the l-l-plane, up to 180, in which, the inner surface is free of scratches or burrs and formed without any flats or sidewall wrinkles in the bend or along the straight sections.

While still another object is to provide a flexible mandrel in which an unlimited number of'elements may be added for the purpose of forming a bend of any dimension desired.

Gther objects and advantages of the present invention will become apparent from an examination of the following detailed description when taken in conjunction with the accompanying drawing, wherein:

H6. 1 is a top-view partially in section illustrating the relative parts of an operating mandrel;

P16. 2 is a view of an individual link such as that which makes up the mandrel shown in FIG. 1;

FIG. 3 illustrates a rear view of the link shown in FllG. 2;

FIG. 4 illustrates a sizing link such as used for the end ele ment of the mandrel; and

FIG. 5 illustrates a rear view of the sizing link.

The mandrel of this invention is formed by a main body to which the first lirik of a plurality of identical body links is connected. The links are connected to each other in succession such that they will pivot relative to each other about a pin that secures the links together. Each of the individual links are formed from a single piece of tool steel such that the links include a main body with a semicircular-shaped lug or tank extending therefrom. The body is formed with a cavity therein which is in the same plane as the lug such that a lug from the adjoining body element will fit into the cavity for rotation about a pin that connects the body elements together. The faces of the body elements paralleling the lug are flat and parallel to each other wherein the ends of each body element are rounded. One end of the face opposite from the lug is cut at an angle such that when the body elements are secured together the mandrel body elements can be rotated relative to each other such that their centers are on a circle in order to form bends in the waveguide. The end body member or sizing shoe is formed with a rectangular body with rounded ends and a lug extending from the body which secures the end body element to the adjacent body element which includes a cavity therein for receiving the lug on the end body member. The sizing shoe is slightly larger than the other body elements for accurately sizing the waveguide and forming a smooth inner surface without any burrs, scratches, or flats.

Now referring to the drawing, there is shown by illustration, a preferred embodiment of the invention. As shown in FIG. 1, the articulated mandrel includes an elongated rectangular main body 10, a plurality of links 11, FlGS. 2 and 3, and a sizing shoe l2, H08. 4 and 5, which is similar to the links 11. The sizing shoe 12 is of rectangular shape with arcuate outer ends 13 wherein the curvature of the arc is in the plane of the width, W. The ends are curved across the entire thickness, of the sizing shoe. The sizing shoe is provided with a connecting tang or lug 14 of semicircular shape which is centrally located with respect to the ends and the thickness of the sizing shoe and parallel with planes along the upper and lower faces l9 and 20. The lug is machined as an integral part of the shoe and is provided with an aperture 15 in the lug for connecting the sizing shoe to its adjacent link ll.

Each of the links ll" are made of rectangular shaped elements with arcuate ends 16 which have the same curvature as that of the sizing shoe. Each link ll is provided with a connecting tang of lug 17, which is the same as for the lug described for the shoe 12, which has an aperture 15 therethrough perpendicular to planes along the upper and lower faces 25 and 26 of the link 11 and to the faces of the lug for connecting each link to each other and for connecting the link adjacent the main body to the main body. Each of the links ll include a centrally located semicircular slot or cavity 18 which extends substantially across the length, l, and which has a slightly larger radius of curvature than the lug 17 for reception of the lug on an adjacent link. The link it is pro vided with an aperture 21 through which a pin 22 is inserted in order to secure the lug 17 of one link to the adjacent link. The aperture 21 is positioned such that the aperture 15 in the lug will align with the aperture 21 and allow freedom of rotational movement of the lug within the slot or cavity such that one end of each of the links moves toward each other, thus each link has relative movement in a plane across the width of and through the center of the mandrel parallel with its upper and lower faces.

Each of the links ll are cut at 20 across the thickness thereof perpendicular to the cavity 113 along one half of the width such that the cutaway portion is from about the center line of the width to the outer end. The cutaway portion may be of any desired angle in order to permit bends when the ends of the links are adjacent to each other. If smaller bends are desired each of the faces on the same end of each link may be tapered which will permit greater movement of the links with respect to each other. Greater movement of the links will permit turns of a less radius. The links are connected to each other and the lug on the end link is connected to the main body. Therefore, the end of the main body to which the end link is connected is of rectangular shape and has a centrally located cavity 23 therein which receives the lug of the adjacent link to the main body.

The main body, each of the links, and the sizing shoe are made of steel and the pins are made with a sheer strength of at least 2,600 pounds even for small size waveguide. The elements may be made for small or larger size waveguide and the elements will function satisfactory for either.

As shown, each of the links and the sizing shoe are made of one piece stock which makes a rugged mandrel. The strength of the mandrel depends on the strength of the sheer pin which may be made of different sizes for different mandrels and with different strengths.

Each of the elements are formed, shaped, polished and made ready for assembly. Since each of the separate links and the sizing shoe are made of one piece stock material, they require only one pin to assemble each successive element together. Any number of elements or links may be assembled together to make a mandrel as long or as short as one desires. The lug on the shaping shoe and each links is sufficiently long that when the links are assembled there will be a spacing between adjacent faces of adjacent links. The spacing and the cut face on the links permits bending the mandrel such that waveguide bends may be made as desired in the H-plane. Making bends in the l-l-plane is made possible since the links pivot about a pin through the link and lug such that relative movement of adjacent links is in a plane through the width parallel with the lugs on the links.

Since the mandrel links are identical and are assembled by use of a single pin, it can be seen that the elements may be added or subtracted as desired. Also the mandrel may be loaded into a waveguide, front or backwards which ever is most convenient for the operator. The unit, once made with the proper number of links may be stored assembled which does not require individual packing procedures as does some mandrel. Such a mandrel provides good right angle corners where walls meet and the sizing shoe being larger than the other links cleans and coins any irregularities in all surfaces. Therefore, an H-plane waveguide with accurate inside dimensions may be formed by use of the above disclosed mandrel.

Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

lclaim: 1. A tube-bending mandrel comprising: a rigid rectangular main body and a flexible body secured thereto; said flexible body including a plurality of pivotally interconnected identical links, and a sizing shoe; each of said links and sizing shoe including substantially rectangular parallel upper and lower faces with a lug projecting from one side thereof; said lug lying in a plane across the midsection of the width parallel with said upper and lower faces; a cavity in each of said links in the side opposite from said lug; said cavity lying in the same plane as said lug and extending toward said lug; an aperture on a center line through said link in the area of said cavity therein perpendicular to said cavity and the jppel and lowerfaces of said links; sar aperture in said link aligning with said aperture "1 said lug of an adjoining link upon insertion of said lug of the adjoining link into the cavity of said adjacent link;

and means for securing said lug within said cavity for relative movement of each of said links in a direction which is in a plane through the center of the links parallel with said upper and lower faces.

2. A tube-bendingmandrel as claimed in claim 1, wherein each ofsaid links has at least one face side out at an angle from the center line to one end thereof.

3. A tube-bending mandrel as claimed in claim 2, in which the sizing shoe is slightly larger than each of said links. 

1. A tube-bending mandrel comprising: a rigid rectangular main body and a flexible body secured thereto; said flexible body including a plurality of pivotally interconnected identical links, and a sizing shoe; each of said links and sizing shoe including substantially rectangular parallel upper and lower faces with a lug projecting from one side thereof; said lug lying in a plane across the midsection of the width parallel with said upper and lower faces; a cavity in each of said links in the side opposite from said lug; said cavity lying in the same plane as said lug and extending toward said lug; an aperture on a center line through said link in the area of said cavity therein perpendicular to said cavity and the upper and lower faces of said links; said aperture in said link aligning with said aperture in said lug of an adjoining link upon insertion of said lug of the adjoining link into the cavity of said adjacent link; and means for securing said lug within said cavity for relative movement of each of said links in a direction which is in a plane through the center of the links parallel with said upper and lower faces.
 2. A tube-bending mandrel as claimed in claim 1, wherein each of said links has at least one face side cut at an angle from the center line to one end thereof.
 3. A tube-bending mandrel as claimed in claim 2, in which the sizing shoe is slightly larger than each of said links. 